The present invention relates to a starting clutch for a continuously variable transmission that also provides for the selection of the power mode for a vehicle or other mobile equipment. Numerous versions of continuously variable transmissions utilizing variable pulleys and a continuous belt are presently known in the prior art, and the generally accepted arrangement for an automotive vehicle utilizes a clutch for a forward-neutral-reverse selector mechanism between the engine or prime mover and the variable pulleys. However, the rate at which the belt can be shifted diminishes as the pulley speed decreases. Also, the vehicle and pulleys must be brought to a complete halt in order to shift from forward to reverse with reversal of the direction of rotation of the pulleys.
To overcome these problems, the clutch and the selector mechanism have been transferred from a location between the engine and the pulleys to a position between the pulleys and the axle ratio and differential to the vehicle wheels, as shown in the Smirl U.S. Pat. No. 4,241,618. In this arrangement, the pulleys are continuously rotated, even at idle rpm, while the engine is running. Initiation of vehicle movement is accomplished by a speed-responsive friction starting device and the power mode, either forward or reverse, attained through a mechanical selector.
Also known in the prior art is the use of a dual clutch arrangement acting in a vehicle transmission. A dual clutch is utilized with each clutch plate being separately hydraulically actuated to provide for the forward speed ratios, reverse and neutral. However, the clutches are used to conjunction with friction brake bands engaging brake drums which operate in conjunction with one or more planetary gear sets. One major problem in this type of arrangement is the amount of drag losses that occur due to incomplete disengagement of the clutches and/or brake bands.
The present invention provides a non-mechanical power mode selector arrangement for a continuously variable transmission without the drag losses previously found in dual clutch transmissions.